Yet her eye problem – likely caused by fatty deposits behind her eyes – is symptomatic of her general obesity which zookeepers in Leipzig now say they are tackling.

“She is making clear progress with mobility, and can now use her tail much better to hold onto things,” said Maria Saegebarth, spokeswoman for the zoo.

She said the opossum's obesity is thought to have been responsible for her eye problem.

Saegebarth said Heidi is becoming more active as she loses weight out of sight of the public in a private area of the zoo. She will be put in the new giant tropical hall which is due to be opened in July.